In reinforced concrete or prestressed concrete components, shear reinforcement is often required in the area of column connections, in particular in the area of prop connectors, in order to absorb the transverse forces occurring due to column forces.
Such shear reinforcement elements are widely known in the form of S-Hooks or stirrups, dowel bars, double-headed bolts, stirrup meshes, open web girders, Tobler Walm®, “Geilinger” collars, and “Riss” stars.
Due to bad anchorage, shear reinforcement in the form of S-hooks or stirrups has to grasp a usually available flexural longitudinal reinforcement in order to prevent the shear reinforcement from being ripped out. The installation procedure is highly time-consuming and therefore also cost-intensive. Conventional stirrups are no longer considered suitable to be fitted at high degrees of reinforcement in the bending tensile reinforcement and at a high proportion of reinforcement.
In the dowel bar known from DE 27 27 159 A1, the dowels are provided with an enlarged dowel head at their end. The dowels are welded at their other end to a dowel support rail. A further development of such a dowel bar is known, for example, from DE 298 12 676 U1. This dowel bar comprises several dowels arranged at a specific distance from one another; these dowels comprise an extended plate-shaped dowel head at one end of the dowel shaft and are attached to a joint dowel support rail at the other end, wherein the respective dowel shaft extends through a dowel drill hole in the dowel support rail, and is provided with a rivet head.
Though such dowel bars are used in diverse ways, practical experience has shown that these dowel bars fail when subjected to strong shear forces because the dowels then become bent. As a result, the connection between concrete and reinforcement becomes loose, and the durability of the concrete component cannot always be provided.
Double-headed bolts comprise a cylindrical bolt and an above or below-lying bolt head which is enlarged in comparison to the bolt and which is generally arranged in the approximate form of a truncated cone. Several such bolts are connected via a distance rail attached at the upper or lower bolt head to a shear reinforcement element, wherein the distance rail ensures correct orientation as well as the correct height position of the double-headed bolts in their state of assembly.
One disadvantage of this shear reinforcement element is that the production of these double-headed bolts is relatively time-consuming and is carried out, by way of example, by clinching the bolt ends to produce the bolt heads or by welding the bolt heads in the form of truncated cones to the bolt.
In addition, the double-headed bolts are usually threaded from above in a star-shaped manner between the upper and lower layer of the longitudinal reinforcement. With high degrees of reinforcement in the bending tensile reinforcement and different mesh openings in the upper and lower reinforcement layer, installation is therefore highly difficult, and is sometimes even impossible.
Tobler Walm® and “Geilinger” Collars are steel mounting components which consist of welded steel profiles and which are individually produced. Movement of the mounting components requires the use of lifting gear due to their high net weight. Production and installation are time-consuming and cost-intensive, as this lifting equipment is not available for other tasks on the construction site or has to be reserved specifically for this task. Due to their size and weight, these solutions cannot be used in prefabricated components, as transportation to the construction site would no longer be cost-efficient. These concrete reinforcement elements are therefore only suitable to be used for concrete components which are produced using on-site mixed concrete.